Charles County staff did not recommend to the county commissioners at their Tuesday meeting any significant changes to a draft ordinance establishing a state-mandated watershed restoration program and associated local stormwater fee.

Local environmentalists proposed a number of modifications to the program at a public hearing last week, including calculating each property’s fee on a case-by-case basis and credits for homeowners who already have installed stormwater mitigation systems on their property, like rain barrels, rain gardens, green roofs and pervious surfaces.

Charles Rice, the county’s environmental program manager, presented alternate methods for calculating the fee for each property, but recommended that the commissioners keep the formula as proposed.

Last year, the Maryland General Assembly passed legislation requiring the state’s 10 largest jurisdictions — which include Charles County — to implement the fee by July 1 to fund projects that reduce stormwater runoff.

The bill came on the heels of a 2010 order from the U.S. Environmental Protection Agency requiring states in the Chesapeake Bay watershed to abide by a “pollution diet” aimed at reducing the amount of pollutants they contribute to the estuary.

Much of the pollution in the bay is attributable to rainwater washing nutrients into the estuary. Properties with the most “impervious surface” generally produce the most runoff.

“Impervious surface” is defined in the state bill as “a surface that does not allow stormwater to infiltrate into the ground” and includes buildings, parking lots, driveways, patios, sidewalks and outdoor athletic courts.

The amount of impervious surface in each jurisdiction has been calculated from a 2011 aerial survey of the state. A county consultant prepared an impervious surface map between July and January.

The impervious surface of each parcel was calculated using the digital map and broken into five classifications — urban single-family homes, townhouses, condominiums, rural residential and agricultural.

The average impervious surface for urban homes was calculated at 3,255 square feet, which was set as the base unit — called an Equivalent Residential Unit — used to calculate the fee for the remaining classifications. For each ERU a property has, $32 will be assessed to its tax bill.

The average impervious surface for townhomes and condos came out to 1,654 and 1,070 square feet, respectively, so in the draft ordinance, each townhome counts as half an ERU and condos are assessed as one-third of an ERU.

Rural homes averaged 7,237 square feet of impervious surface and are each assessed two ERUs. Farm properties also count as two ERUs, despite averaging 10,003 square feet of impervious surface.

Nonresidential properties, such as commercial, industrial, mixed-use or faith-based institutions, and apartment buildings, are allotted ERUs on a case-by-case basis. On average, the county’s commercial properties would be assessed 13 ERUs under the ordinance, while industrial properties would average 18 ERUs, apartment buildings would average 40 and faith-based institutions would average 14.

Rice noted that at the public hearing, “there was some confusion” about why rural homes and farmland received more ERUs than urban homes, even though they tend to have more pervious surface area that soaks up runoff, such as fields and forestland.

“When you look at the actual impervious surface, rooftops for example, on those properties, because a farm potentially has many barns, sheds, silos, other infrastructure other than just a single-family dwelling, the impervious surface footage really adds up,” Rice said.

Rather than a reduction in the stormwater fee, Rice said that the county is instead offering rebates on “stormwater best management practices” in order to encourage property owners to install them on their own.

The administrative cost in calculating a reduced fee for individual homeowners would “far exceed” the savings, Rice said. However, nonresidential properties will be eligible for a credit because their fee already will be calculated on a case-by-case basis.

“I have a problem with one size fitting all, and I also think that the rebates are great, but I think properties that are already employing best practices or choose to employ best practices to reduce their runoff deserve a reduction in the fee,” Commissioner Ken Robinson (D) said.

Commissioners’ Vice President Reuben B. Collins II (D) agreed, stating he would like to see the county’s policy “give some type of credit for best practices,” while adding that some jurisdictions have offered waivers to farmers.

Commissioners’ President Candice Quinn Kelly (D) also backed the idea of a credit for those who have spent money to mitigate stormwater runoff on their property.

Rice said the positives to structuring the fee like Howard County, which will charge $15 for every 500 square feet of impervious surface a property has, is that it is more equitable and specific to individual properties.

But he noted that such a program requires continuous revision, as each property’s amount of impervious surface can change with the addition of a driveway, shed, patio or pool. As a result, the amount of appeals filed would increase and the expenses would pile up, Rice said.

“The practice of averaging it out helps reduce the burden overall,” he added.

Rice also touched on the “somewhat interesting” approach to the fee in Frederick County, which is charging 1 cent per property in order to abide by the statute, with plans to fund the program by some other method.

Rice reviewed comments received following the public hearing — many of them from people who testified at the forum — before offering staff’s recommendations, which amounted to short clarifications rather than wholesale changes.

Commissioner Debra M. Davis (D) expressed concern that the commissioners might be running close to the time that they need to pass legislation in order to have the fee implemented by the deadline, but said that a recent conversation with Sen. Thomas “Mac” Middleton (D-Charles) left her feeling confident that the county could get an extension if it needed one.

“I can’t even tell you right now that I understand it or have enough grasp of it to even make a logical decision,” she said.

County Attorney Barbara Holtz said she believed the state could make “reasonable accommodations” for counties that show they are well on their way to implementing the fee, but stressed that, under the state law, the county could be fined between $1,000 and $20,000 for each day past July 1 that it doesn’t have the program in place.

Rice said that even if the fee isn’t settled by July 1, the county still could fund the program by increasing its existing environmental service fee.